Photomask Registration Error Correction via Laser Stress Generation
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Solution Overview
Problem
Photomask registration errors occur due to positional inaccuracies during the fabrication process, leading to non-uniform optical pattern formation, which affects the accuracy and reliability of semiconductor devices, and existing methods are inadequate for correcting severe errors without discarding defective photomasks.
Innovation Solution
The introduction of stress generation portions in the photomask substrate, formed by irradiating a laser beam, which correspond to measured registration errors, either expanding or contracting the substrate to correct positional discrepancies, thereby aligning optical patterns accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photomask is fabricated using electron beam lithography with stage movement, then optical patterns can be formed on the photomask substrate, but positional errors occur during stage movement leading to registration errors in the optical patterns
Solution Approach 1:
The patent replaces the mechanical stage movement system with a direct-write electron beam system. Instead of moving the stage to position the electron beam, the electron beam is directly scanned and positioned on the photomask substrate using electromagnetic deflection fields. This eliminates mechanical positioning errors and registration inaccuracies caused by stage movement, while maintaining the ability to form optical patterns with high precision.
2Reliability
If photomask registration errors are severe, then the photomask must be discarded, but this results in loss of manufacturing resources and increased production costs
Solution Approach 1:
The patent implements preliminary correction actions by forming compensation patterns during the initial electron beam lithography process. Registration errors are predicted and compensated for by adjusting the electron beam positioning in advance, allowing the photomask to be corrected before final fabrication. This prevents the need to discard photomasks with registration errors, reducing waste and manufacturing costs.
3Productivity
If the stage moves rapidly to increase productivity, then production time is reduced, but positional errors increase leading to registration inaccuracies
Solution Approach 1:
The patent eliminates the mechanical stage movement system and replaces it with a stationary substrate and directly scanned electron beam. The electron beam is positioned using electromagnetic deflection fields that can rapidly change position without mechanical inertia or vibration. This allows for high-speed pattern formation while maintaining precise positioning accuracy, as the beam can be redirected instantaneously without the acceleration and deceleration limitations of mechanical stages.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively corrects registration errors in photomasks, enhancing the yield, productivity, and reliability of semiconductor devices by allowing the use of previously defective photomasks, reducing manufacturing costs and shortening production time.
Implementation Method 1
forming stress generation portions in the photomask substrate by irradiating a laser beam
Implementation Method 2
either expanding or contracting the substrate to correct positional discrepancies
Data Source
AI summary
Provided are photomask registration errors of which have been corrected and a method of correcting the registration errors of a photomask. The photomask includes a photomask substrate, an optical pattern formed on one surface of the photomask substrate, and a plurality of stress generation portions formed in the photomask substrate. A method of correcting the registration errors of a photomask includes the steps of forming an optical pattern on a photomask substrate, measuring the registration errors of the optical pattern, and forming a plurality of stress generation portions in the photomask substrate so that the stress generation portions correspond to the measured registration errors.